Read the full version in this print feature in the Saturday/Sunday, March 2-3, 2019 edition of the Wall Street Journal.

Cities the world over are having a garbage crisis, or more specifically, a recycling crisis.

In 1950, the world produced about 4 billion pounds of plastic a year. Today, we produce about 600 billion pounds. Every year, about 20 billion pounds of it ends up in the ocean. Over 90% of produced plastic has never been recycled, and it typically takes more than 400 years to break down naturally.

From Australia to Japan, New York City to Hong Kong, garbage collectors are being forced to make a mockery of those curbside recycling bins we have all been trained to fill. In Philadelphia, for example, the city currently burns 200 tons of recyclables a day—half of what it collects. The result is an increase in carcinogens spewing into the air around the city’s incinerator in nearby Chester, Pa.

A trash startup, Rubicon, was recently valued at more than $1 billion.

The reason this problem is coming to a head now is China. Its “National Sword” policy, designed to help it deal with its own towering mountains of waste, last year declared an end to the country accepting “loathsome foreign garbage.” Before the policy came into effect, China imported about 40% of America’s recyclables, and an even greater proportion from other countries, to feed its insatiable need for raw materials.

Another unexpected cause is fracking, and the consequent nosedive in the cost of natural gas starting in 2014. One product of natural-gas refining is “virgin resin,” the plastic feedstock manufacturers use to make pretty much any plastic you can name.

It’s a crisis so big that no amount of technology, innovation or policy can solve it in the near future—but that’s not stopping a litany of trash-tech companies from trying, including the market’s first unicorn, Rubicon, recently valued at more than $1 billion.

Rubicon, which serves as a marketplace for to connect haulers and businesses, is used by more than 30 U.S. municipal and state governments to help them identify where their streams of recyclables are being contaminated. The company’s “Flash” technology replaces manual counts of foreign material with images snapped on mobile devices used by garbage collectors.